• Title, Summary, Keyword: very broadband seismic station

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Installation of Very Broadband Seismic Stations to Observe Seismic and Cryogenic Signals, Antarctica (남극 지진 및 빙권 신호 관측을 위한 초광대역 지진계 설치)

  • Lee, Won-Sang;Park, Yong-Cheol;Yun, Suk-Young;Seo, Ki-Weon;Yee, Tae-Gyu;Choe, Han-Jin;Yoon, Ho-Il;Chae, Nam-Yi
    • Geophysics and Geophysical Exploration
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    • v.15 no.3
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    • pp.144-149
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    • 2012
  • Korea Polar Research Institute (KOPRI) has successfully installed two autonomous very broadband three-component seismic stations at the King George Island (KGI), Antarctica, during the 24th KOPRI Antarctic Summer Expedition (2010 ~ 2011). The seismic observation system is originally designed by the Incorporated Research Institutions for Seismology Program for Array Seismic Studies of the Continental Lithosphere Instrument Center, which is fully compatible with the Polar Earth Observing Network seismic system. The installation is to achieve the following major goals: 1. Monitoring local earthquakes and icequakes in and around the KGI, 2. Validating the robustness of seismic system operation under harsh environment. For further intensive studies, we plan to move and install them adding a couple more stations at ice shelf system, e.g., Larsen Ice Shelf System, Antarctica, in 2013 to figure out ice dynamics and physical interaction between lithosphere and cryosphere. In this article, we evaluate seismic station performance and characteristics by examining ambient noise, and provide operational system information such as frequency response and State-Of-Health information.

Monitoring North Korea Nuclear Tests: Comparison of 1st and 2nd Tests (북한 핵실험 모니터링 : 1, 2차 비교)

  • Chi, Heon-Cheol;Park, Jung-Ho;Kim, Geun-Young;Che, Il-Young;Sheen, Dong-Hoon;Shin, Jin-Soo;Cho, Chang-Soo;Lee, Hee-Il
    • Geophysics and Geophysical Exploration
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    • v.13 no.3
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    • pp.243-248
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    • 2010
  • Two suspicious events, which were claimed as underground nuclear tests by North Korea, were detected in the northern Korean Peninsula on October 9, 2006 and May 25, 2009. The KIGAM and Korea-China Joint seismic stations are distributed uniformly along the boundaries between North Korea and adjacent countries. In this study, the data from broadband stations with the distance of 200 to 550 km from the test site are used to analyze and compare two nuclear tests of North Korea. By comparing the time differences of the Pn-wave arrival times of 1st and 2nd tests at multiple stations, the relative locations of two test sites could be calculated precisely. From the geometrical calculation with the velocity of Pn wave $V_{Pn}$ = 8 km/s, the 2nd test site is estimated to move in the WNW direction from 1st one with the distance of 2 km. Body wave magnitude, mb of the 2nd test, which was announced officially as the network average of 4.5, varies widely with the directional location of stations from 4.1 to 5.2. The magnitude obtained from Lg wave, $m_b$(Lg), shows less variation between 4.3 to 4.7 with the average of 4.6. The moving-window spectra of time traces of 1st and 2nd tests show very similar pattern with different scale level. In addition, the corner frequencies of P wave of 1st and 2nd tests at each station show no or negligible difference. This indicates the burial depths of two tests might be very similar. The relative yield amount of the 2nd test is estimated 8 times larger than that of the 1st from the weighted average of ground-velocity amplitude ratios.